WASHINGTON - After falling steadily for more than a decade, the birth rate for American teenagers jumped last year for the first time since 1991, health officials reported yesterday, a sharp reversal in one of the nation's most celebrated social and public health successes.

The birth rate among girls 15 to 19 years old rose 3 percent between 2005 and 2006, after plummeting 34 percent over the previous 14 years, the National Center for Health Statistics reported.

Stephanie Ventura, who heads the center's reproductive statistics branch, described the data as "concerning" but said it is too soon to know whether the increase was the beginning of a trend. But she said the magnitude of the rise was worrisome.

"This early warning should put people on alert to look at the programs that are being used to see what works," Ventura said.

While the cause of the reversal was unclear, it reignited debate about abstinence-only sex education programs, which receive about $176 million a year in federal funding; Congress is now debating the addition of $28 million more.

Some experts blame the rise of the teen birth rate on these programs, saying they do not teach use of condoms and other contraception.

The teen birth rate rose sharply between 1986 and 1991, when it hit an all-time high of 61.8 births per 1,000 girls. The increase led to a massive campaign to counter the trend, and the rates of both teenage sexual activity and teen births began falling.

The new data show an increase from 40.5 births per 1,000 girls in 2005 to 41.9 per 1,000 in 2006. The rate rose among all races.